<style>
    tr:nth-child(2n){background-color:blue;}
    td:nth-child(2n){background-color:red;}
    tr:nth-child(2n)>td:nth-child(2n){background-color:yellow;}
    
</style>
<?php

    //PHP双循环 5行3列
    
    
    echo '<table border=1>';
    
    //外循环负责行
    for($i=1;$i<=15;$i++){
      
        echo '<tr>';
            
           
            for($j=1;$j<=10;$j++){
                echo '<td>xxoo</td>';
            }
        echo '</tr>';
    }
    echo '</table>';


?>